1. Field of the Invention
The present invention relates to aircraft control surfaces and, more particularly, to a system for operating an aircraft control surface such that a maximum mechanical advantage of the actuating mechanism is achieved when the control surface is also at its maximum deflected position.
2. Prior Art
The typical wing design for an aircraft includes a primary wing surface, or airfoil, having a leading edge and a trailing edge with a control surface located at the leading and trailing edges of the wing. Flaps and ailerons are both examples of control surfaces, with flaps being designed to increase wing lift and ailerons used for roll axis control. The flaps on each wing operate in unison to increase wing lift by increasing the camber of the wing. By comparison, ailerons are pivoted oppositely to increase lift on one wing while reducing lift on the opposite wing to induce a rolling moment. Similarly, elevator sections of the horizontal tail are pivotably attached to the fixed tail section to vary lift and provide pitch control.
When either the flap or the aileron is activated, the control surface rotates relative to the trailing edge of the wing. Control surfaces are typically rigid structures which maintain their shape throughout rotation. Therefore, gaps or abrupt changes occur at the hinge area of a conventional control surface. This gap increases the drag and lowers the efficiency of the control surface. Additionally, as the control surfaces are rotated, gaps are formed between the ends of the hinged control surface and the adjacent portions of the fixed wing.
A number of patented constructions typify the current state of the art. in regard, both, to the actuating mechanisms and to the desirability of minimizing the effect of discontinuities occurring between the control surface and the wing or fixed airfoil to which the control surface is movably attached. For example, U.S. Pat. Nos. 2,670,909 to Replogle and 5,161,757 to Large both disclose actuating mechanisms for an aircraft control surface in the form of a flap. The flap both rotates and extends relative to the primary airfoil. In each instance, the actuating mechanism employs a xe2x80x9chornxe2x80x9d or bent shaft within the flap body that rotates about an axis normal to the trailing edge. However, in each instance, the patented mechanism operates only in a downward direction.
U.S. Pat. Nos. 3,944,170 and 4,286,761 both to Musgrove disclose an eccentric actuator that provides rotation of a flap body.
U.S. Pat. No. 5,222.699 to Albach et al. and assigned to the assignee of the present invention discloses a variable contour aircraft control surface which employs elastomeric transition sections between inboard and outboard edges of the variable contour control surface and a main wing portion. The transition sections include thick elastomeric layers with oversized holes therein and rods positioned in the oversized holes. Some of the rods are attached to the main wing portion while others of the rods are attached to the control surface.
U.S. Pat. No. 3,109,613 to Bryant et al. discloses a variable camber device that recambers the entire aft portion of the wing structure. It maintains a xe2x80x9cseamlessxe2x80x9d hinge line by employing a sliding skin joint, but it does not maintain seamless edges.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
The present invention relates to a flight control system which provides a maximized mechanical advantage when the load of the airstream on the airfoil is also at a maximum. A control surface is mounted on the airfoil for pivotal movement about a spanwise extending axis through a range of positions between a neutral position at which airstream load thereon is a minimum and an upwardly deflected position, in one instance, and a downwardly deflected position in another instance, the airstream load on the control surface being a maximum in either the upwardly deflected position or in the downwardly deflected position. An operator mechanism for moving the control surface between the upwardly deflected and downwardly deflected positions includes a rotor mounted on the airfoil for rotation about a chordwise extending rotary axis and has a horn member with a terminal end offset from the rotary axis. The terminal end of the horn member is slidably engaged with the guide track generally in the plane of the airfoil and an actuator serves to rotate the rotor about the rotary axis and by reason of the slidable engagement of the terminal end of the horn member with the guide track thereby moves the control surface between the upwardly deflected and downwardly deflected positions.
A primary feature, then, of the present invention is the provision of a flight control system for an aircraft according to which a maximum mechanical advantage of the actuating mechanism for an aircraft control surface is achieved when the control surface is also at its maximum deflected position.
Another feature of the present invention is the provision of such a flight control system according to which the aircraft wing structure includes a control surface that allows for variable camber of the wing while eliminating any gap or abrupt change between the trailing edge of the wing and the joining edges of the control surface.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.